Metal (typically steel) posts or pickets are commonly employed for temporary fencing measures, and most commonly feature a T-shaped, t-shaped, Y-shaped, or star-shaped cross section. In a common temporary fencing setup, a series of posts are driven into the ground at spaced apart positions along the intended fence line, and then wire mesh is strung up between adjacent posts using a series of teeth that are provided on a flange or web of the post. When it becomes desirable to take down or relocate the fence, the mesh is removed and rolled up, and the posts are pulled free of their previously embedded positions in the ground.
A number of devices have been previously proposed for the purpose of pulling posts from the ground, including those disclosed in U.S. patents U.S. Pat. No. 1,774,661, U.S. Pat. No. 4,422,621, U.S. Pat. No. 4,721,335, U.S. Pat. No. 5,011,117, U.S. Pat. No. 5,368,277, U.S. Pat. No. 7,059,587, U.S. Pat. No. 7,290,754, U.S. Pat. No. 7,963,051, U.S. Pat. No. 8,608,132 and U.S. Pat. No. 8,453,993; U.S. Patent Application Publications US2007/0183121, US2012/0279737 and US20090028649; and PCT Publication WO2012116405.
Of these references, U.S. Pat. No. 1,774,661 and U.S. Pat. No. 8,453,993 employ a cam-based post gripping mechanism that is most comparable to that of the present invention, but rely on manual levers to provide the post gripping and pulling forces required to grip the post and pull it free from the ground. Other references make use of external equipment to provide the lifting and gripping force, but not in a manner compatible with a cam-based gripping mechanism like that employed in the present invention.
Applicant has therefore developed a unique solution for actuating post grippers of a post puller using a skid steer, front end loader, excavator, back hoe or other working machine with a powered lifting arrangement.